Observation and analysis of SAO76103 in Sep. 10, and Dec1. 2009 (UTC)

Oct. 24, 2009
reviced Jan. 11, 2010
Kazuhisa Miyashita

in Japanese

Doublestar Report to IOTA coordinator

Two occultation events of this star were observed in Sep. 10, 2009. And in the other oppotunity, Dec. 1, Karasaki-san who also observed this star in Sep. 10 observed it again. From this, an astrometric analysis become to be possible.

Observation details

          September 10, 2009                    December 1, 2009      
H. Karasaki            M. Ishida                H. Karasaki   
Star Mag = 7.93        Star Mag = 7.93          Star Mag = 7.93
   Event = R D            Event = R D              Event = D D
      PA = 240.950           PA = 242.860             PA = 84.320
      AA = 254.501           AA = 256.410             AA = 98.141
           l = -4.430             l = -4.409               l = -4.309
       b = -5.183             b = -5.175               b = -5.096
      RV = 0.5282            RV = 0.5425              RV = 0.4098
     CCT = -170.60          CCT = -172.30            CCT = -13.50
      T1 = 54.75             T1 = 52.49               T1 = 50.20
   T2-T1 = -0.05          T2-T1 = -0.07            T2-T1 = -0.07

Occultation timing report

Place name     Nerima, Tokyo, Japan
Email address  
Representative Hideyoshi Karasaki

TB  CED   20   146  +13940xx.x  +3544xx.x  84   xx  M
TC  CED   20   454  +1394001.2  +3544xx.x  84   xx  M

OA  H. Karasaki               

20090910140854.70 X  4786 RD     EG G0.02 1   W      222   BA
20090910140854.75 X  4786ARD     EG G0.02 1   E      222   BA


20091201120750.27 X  4786 DD     EG G0.04 1   W      31    CA
20091201120750.34 X  4786 DD     EG G0.02 1   E      31    CA

-------------------------------------------------------------

Place name     Matusaka, Mie, Japan
Email address  
Representative Masayuki Ishida

TA  NED   16   100  +13628xx.x  +3435xx.x  84   xx  M

OA  M. Ishida                 

20090910140652.41 S 76103 RD     EG G0.04 1   W      11    AA
20090910140652.48 S 76103 RD     EG G0.04 1   E      11    AA

Light curve and Explanation

i) Karasaki's observation (Sep. 10, 2009)




Karasaki-san (Mr. Hideyoshi Karasaki) observed xz4786, and he found a small step on the lightcurve. As a result of my confirmation analysis, the 3D graoh at the intermediate value shows the appearance of a faint star, and the diffraction simulation indicates that the event could not make gradual light change. From this, it is thought that the step is generated by a double star which consists of two similar magnitude stars.

ii) Ishida's observation

Ishida-san (Mr. Masayuki Ishida) also observed SAO76103 occultation and sent me his video file. The video is noisy, so I used small (4 pixel radius) aperture to reduce the background noise, and I obtained Limovie graph. There is a small step at No.252 and 253 frame. It is also confirmed from the image of a faint star on the 3D-graph of 252 (253) frame. Additionally, the RV is 0.5425, therefore it is difficult to think that the step is generated from diffraction tail with noise. Although the step height is different from Karasaki-san's observation, I think the light curve (and 3D graph) indicates that there is a component of closed double.
iii) Karasaki's observation (Dec. 1, 2009)

Karasaki-san, who is one of the observer of above occultation event, had observed same star again and found small step on the light curve. I also analyzed his video with Gaussian noise reduction filtre and confirmed the step. I think this step like light change is not a diffraction tail.

Photometry

i) Karasaki's observation (Sep. 10, 2009)


ii) Ishida's observation
- Estimation of Magnitude of Doublestar Components -

Assuming magnitude of Pair is  7.93 Mag.
Estimated Magnitude
  First Event  :  9.49 +/- 0.13  Mag.
  Second Event :  8.22 +/- 0.05  Mag.
- Measurement ---------------------------------------

Luminous Intensity derived from Limovie analysis
               Average   Stdv      n
  Combined  :  1110.1    235.5    120 
  Step      :   280.7     40.6      2 
  Background:    22.2     68.3    120
Noise Level (N/S)
               Upper  Lower
  First event: 0.1570   0.2643        
  Second event:0.2839   0.0489  

i) Karasaki's observation (Dec. 1, 2009)


From IOTA coordinator

[Jan. 10, 2010]
Thank you for the report of the observation of S76103 by Karasaki-san.
With his earlier observation and the one by Ishida-san on September 10 it is possible to get a solution for the position angle and separation of the pair:
PA = 163.0±2.6° separation = 0.139±.026".
I have attached the solution as generated by Occult.
The two magnitude determination by Karasaki-san also match well: 8.60+8.77 in September and 8.60+8.78 for this observation. It is strange that the magnitudes by Ishida-san appear so different: 8.23+9.48.

Brian

IOTA coodinator's astrometry

[Sep. 14, 2009]
Hello,

Thanks for the two reports on the occultation of S76103. My thanks also to Karasaki-san.

While both look to suggest the observation of a double, the difference in magnitude steps does raise problems. Further observations would be very useful.

The two observers are too close in event PA for a useful determination of the separationa dnPA of the pair. However it looks as if they are closer than the extrapolated 0.9" separation which suggests a 1.7 second time difference.

There are 2 opportunities for Japan, 2009 Dec 1 and 2010 Jan 25. Also 2009 Nov 4 for SE USA, 2009 Dec 28 Europe. During 2010 the occultations move south, but are poorly placed. 2011 Jan 15 may be possible from Australia, after which they cease.

Brian